The invention relates to a kit of parts for a modular femur head prosthesis, in particular a reoperation prosthesis comprising a distal shaft part to be anchored in a femur bone and a neck part which can be fixed to the proximal end portion of the shaft part by means of a screw connection, and can be equipped with an artificial ball.
Moreover, the invention relates to a femur head prosthesis assembled from such a construction kit.
A femur head prosthesis of the named kind is known from EP 0 399 920 A1 and comprises a shaft part having an outside thread and a proximal extension in the shape of a truncated cone and a neck part which can be mounted on the shaft part and which has a slip-on mandrel for the joint ball, with the mandrel being inclined with respect to the longitudinal axis of the shaft part. The neck part is held so that it can be clamped against the extension of the shaft part by a securing screw which can be screwed into an axial bore of the shaft part or of an insert part connected to it. The shaft part of the known endoprosthesis is provided with tongue-like, outwardly deployable segments in a longitudinal section of its axial bore. The segments can be clamped radially outwardly against the piece of femur surrounding the shaft part, in each case relative to two neighbouring fixed segments of the shaft part, by an adjusting means which can be introduced into the bore in the axial direction and which has wedge-shaped supporting surfaces. The main loading forces to be transferred to the femur are in each case respectively introduced into the femur shaft prosthesis by way of the joint ball which is laterally displaced with respect to the longitudinal axis of the shaft part. Accordingly, femur shaft prostheses of the type mentioned are stressed in each case by relatively large dynamic forces and bending moments. With the previous endoprostheses of the type mentioned, dynamic stresses or loads of this kind can lead to a loosening of the screw connection between the neck part and the shaft part and/or to a loosening of the anchoring of the shaft part in the femur bone and can, as a result, lead to high local stresses of the bone tissue, for example, in the region of a dowel-like spreading of the shaft part.